serial: mxs: Add MXS AUART driver

Add trivial driver for the MXS AUART IP. This is the other UART IP
present in i.MX23 and i.MX28, used to drive the non-DUART ports.

Signed-off-by: Marek Vasut <marex@denx.de>
diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index f4767c8..a1e0899 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -966,6 +966,14 @@
 	  Driver works in FIFO mode.
 	  Multiple baudrates supported.
 
+config MXS_AUART_SERIAL
+	bool "MXS AUART"
+	depends on DM_SERIAL
+	help
+	  Support for Freescale i.MX23 / i.MX28 AUART or Application UART IP.
+	  This IP is present in the aforementioned SoCs, however this is not
+	  the IP used to drive the Debug UART port, for that see PL01X_SERIAL .
+
 config OCTEON_SERIAL_BOOTCMD
 	bool "MIPS Octeon PCI remote bootcmd input"
 	depends on ARCH_OCTEON